Genetics

Question 1

Codominance

Answer 1

Multiple alleles are simultaneously expressed.

Ex: ABO blood types

Question 2

Incomplete Penetrance

Answer 2

Individuals who carry mutant genotype but do not express it

Ex: BRCA1

Question 3

Variable Expressivity

Answer 3

Variability in a phenotype

Ex: NF1

Question 4

Pleiotropy

Answer 4

One gene is responsible for many manifestations

Ex: Homocystinuria

Question 5

Anticipation

Answer 5

The tendency of disease to occur in earlier in each generation.

Ex; Huntington

Question 6

Loss of Heterozygosity

Answer 6

tumor suppression genes must be mutated on both chromosomes to cause cancer.
Ex: Rb

Question 7

Germline Mosaicism

Answer 7

Multiple distinct cell lines in the gametes, but not somatic cells

Question 8

Somatic Mosaicism

Answer 8

Gametes are normal, but somatic cells are affected.

Question 9

Locus Heterogeneity

Answer 9

The same phenotype can be caused by mutations at different genes.
Ex: Albinism

Question 10

Allelic Heterogeneity

Answer 10

The same phenotype can be caused by different mutations within the same gene.
Ex: B Thalassemia

Question 11

Heteroplasmy

Answer 11

Presence of both mutated and normal mitochondrial genomes within the same cell.

Question 12

Impriniting

Answer 12

Methylation of cytosine by SAM
Can cause disease if there is a mutation in the opposite chromosome
Ex: Prader-Wili/Angelman Syndrome

Question 13

Prader-Wili Syndrome

Answer 13

Chromosome 15
PWS gene from father is mutated or deleted
Obesity, hyperphagia, ID, hypogonadism, hypotonia, temp instability

Question 14

Angelman Syndrome

Answer 14

Chromosome 15
Maternal UBE3A gene is normally actived but is deleted in this syndrome.
Inappropriate laughter, ID, seizures, ataxia

Question 15

Uniparental Disomy

Answer 15

Two copies of the same chromosome are inherited from the same parent.

Question 16

Features of autosomal dominant disorders

Answer 16

Male to male transmission

Question 17

Skewed lyonization

Answer 17

XXd but the healthy X becomes a bar body so the carrier state is converted to a disease state.

Question 18

Achondroplasia

Answer 18

FGFR3 Mutation
chondrocyte proliferation impairment
most common cause of dwarfism
85% due to sporadic mutation (advanced paternal age) 
15% autosomal dominant

Question 19

Acute Intermittent Porphyria

Answer 19

Autosomal Dominant
Mutation is porphobilinogen deaminase
Abdominal pain, neuropathy, psych issues
Increased urinary porphobilinogen

Question 20

NF1

Answer 20

Autosomal dominant
Chromosome 17
Cafe au lait spots, freckles, Lisch nodules, pheochromocytoma, and optic pathway gliomas.
Variable expression but 100% penetrance

Question 21

von Hippel Lindau

Answer 21

VHL gene on chromosome 3. Autosomal dominant.

RCC, hemangioblastoma. and pheochromocytoma.

Question 22

Try hunting for my fragile eggs

Answer 22

Trinucleotide repeat mnemonic
Huntingtons
Friedreich ataxia
Myotonic dystrophy
Fragile X syndrome

Question 23

Huntington

Answer 23

Autosomal dominant
CAG repeats (glutamine)
basal ganglia atrophy
decreased Ach, GABA
increased dopamine

Question 24

Friedreich Ataxia

Answer 24

Autosomal Recessive
GAA repeat (GAit Ataxic)
Mitochondrial dysfunction
Neurologic deficits, DM, cardiomyopathy

Question 25

Myotonic Dystrophy

Answer 25

Autosomal Dominant
CTG (Cataracts, Tired Muscles, Gonads)
Myotonin protein kinase deficiency

Question 26

Fragile X Syndrome

Answer 26

X linked dominant
CGG (Chin, Gonads, Gene silencing)
Long face, long jaw, neurpsych problems, joint hyperlaxity, macroorchism
Most common cause of inherited ID

Question 27

William Syndrome

Answer 27

Microdeletion on chromosome 7

Elfin face, very friendly, intellectual disability

Question 28

DiGeorge’s Syndrome

Answer 28

Microdeletion on chromosome 22
CATCH-22
Cleft palate, abnormal facies, hypertelorism/T cell deficiency, cardiac defects, hypocalcemia

Question 29

Histone molecules

Answer 29

H2 H3 H4 are the core, H1 is outside the core and binds the linker DNA.

Question 30

Polygenic inheritance

Answer 30

Androgenetic alopecia, epilepsy, glaucoma, HTN, ischemic heart disease, schizophrenia, DM2

Question 31

TTN gene

Answer 31

Titin gene
hereditary dilated cardiomyopathy
Autosomal dominant but incomplete penetrance